A teenage schoolboy died in a blood-soaked scene which resembled a horror film, the trial of his alleged killer heard today.

Popular student Jimmy Mizen died after he was struck by a glass dish which smashed and cut blood vessels in his neck sending blood squirting all over a baker's shop.

The row which led to the 16-year-old's death was no more than a trivial incident that resulted in "three minutes of absolute madness", prosecutor Crispin Aylett told the Old Bailey.

Aylett said his accused killer Jake Fahri, 19, had become enraged when Mizen would not move out of his way.

"It seems extraordinary that a young man might go into a baker's on a Saturday morning and end up dead but that is what happened," he said.

Fahri was seen running away "smirking", he added.

The court heard Fahri had begun reaching for weapons and had smashed down the front doors of the bakery with an advertising hoarding before finally grabbing the glass Pyrex dish.

A shard of glass from the dish cut into Mizen's neck and into the jugular vein and severed a major artery.

"One of the staff at the bakery has described it as being like a horror film -- blood was spurting from Jimmy's neck," Aylett said.

Mizen, one of nine children, had gone into the Three Cooks Bakery near his home in Lee, south London, the day after his birthday in May last year with his older brother Harry.

After Fahri carried out the attack, their elder brother Tommy was summoned. He arrived in time to cradle Jimmy in his arms as he was dying, the court heard.

Mizen's mother, Margaret, rushed to the shop and fainted when she saw what happened.

Fahri denies murder and the trial, expected to last three weeks, continues.